The major objective of this work is the application of digital computers to the derivation of synthetic pathways to complex organic structures. A general problem-solving program, LHASA (Logic and Heuristics Applied to Synthetic Analysis), is being developed which can be used interactively by a chemist with simple graphical input-output of structural formulas. The principles and strategies of organic synthesis are being formalized for use by the program. A variety of strategies including long-range search capabilities are being employed in the program. In addition, the vast range of information on synthetic chemistry is being organized and rationalized to provide a rich and effective database. The program can be applied to problems involving biologically important substances and is being made available for general use.